From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F37FAC4338F for ; Fri, 20 Aug 2021 18:41:27 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B74B660FE8 for ; Fri, 20 Aug 2021 18:41:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B74B660FE8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=AP5Cu6rmYTeD6eRoe2i+OhyFSRd2fra1pSntFSbnQ/U=; b=Q69m50/Pe2/2Ep NzWdp437Jmn90lKu9+B2DpD21b8WdY27K0ZtJXfFuMq69dxohZxzwKZ218YEsdYB0BCuRCAko/mug oNPBolHoIZpxXgmS34m2Y1/X2h23SnBjBKWxs45mONl9oOb/kdt3NvZe4SdnvdPRDI7kx/9jvcfs/ vnnssnrd29T+38rgGpQd5cm5MImUGP3dCYOJy+DNRPX6hDhaPj7cOtQyabRNWbFXEkYnppNjp5FDj +pu1+B0rLTPycUBcOF//CkNYlaTYJUnh+RujWqOth9p/CcZqUEPDDUoCHZHzoR6sRv9wcb6kottK2 pje1wYP1CGdr8vXVNClQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mH9Rz-00Bukh-0U; Fri, 20 Aug 2021 18:41:07 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mH9Rv-00Bujr-L5 for linux-riscv@lists.infradead.org; Fri, 20 Aug 2021 18:41:05 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 505A760232; Fri, 20 Aug 2021 18:41:03 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mH9Rt-006GBI-8C; Fri, 20 Aug 2021 19:41:01 +0100 Date: Fri, 20 Aug 2021 19:41:00 +0100 Message-ID: <87bl5syn5v.wl-maz@kernel.org> From: Marc Zyngier To: Matteo Croce Cc: Eric Dumazet , Thierry Reding , netdev@vger.kernel.org, Linux Kernel Mailing List , linux-riscv , Giuseppe Cavallaro , Alexandre Torgue , "David S. Miller" , Jakub Kicinski , Palmer Dabbelt , Paul Walmsley , Drew Fustini , Emil Renner Berthing , Jon Hunter , Will Deacon Subject: Re: [PATCH net-next] stmmac: align RX buffers In-Reply-To: References: <20210614022504.24458-1-mcroce@linux.microsoft.com> <871r71azjw.wl-maz@kernel.org> <202417ef-f8ae-895d-4d07-1f9f3d89b4a4@gmail.com> <87o8a49idp.wl-maz@kernel.org> <20210812121835.405d2e37@linux.microsoft.com> <874kbuapod.wl-maz@kernel.org> <87wnohqty1.wl-maz@kernel.org> <87fsv4qdzm.wl-maz@kernel.org> <87mtpcyrdv.wl-maz@kernel.org> <87h7fkyqpv.wl-maz@kernel.org> <87fsv4ypfn.wl-maz@kernel.org> <87eeaoyon3.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: mcroce@linux.microsoft.com, eric.dumazet@gmail.com, thierry.reding@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, peppe.cavallaro@st.com, alexandre.torgue@foss.st.com, davem@davemloft.net, kuba@kernel.org, palmer@dabbelt.com, paul.walmsley@sifive.com, drew@beagleboard.org, kernel@esmil.dk, jonathanh@nvidia.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210820_114103_763195_867878D9 X-CRM114-Status: GOOD ( 42.61 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, 20 Aug 2021 19:14:22 +0100, Matteo Croce wrote: > > On Fri, Aug 20, 2021 at 8:09 PM Marc Zyngier wrote: > > > > On Fri, 20 Aug 2021 18:56:33 +0100, > > Matteo Croce wrote: > > > > > > On Fri, Aug 20, 2021 at 7:51 PM Marc Zyngier wrote: > > > > > > > > On Fri, 20 Aug 2021 18:35:45 +0100, > > > > Matteo Croce wrote: > > > > > > > > > > > > I think it's wrong. The original offset was 0, and to align it to the > > > > > > > boundary we need to add just NET_IP_ALIGN, which is two. > > > > > > > NET_SKB_PAD is a much bigger value, (I think 64), which is used to > > > > > > > reserve space to prepend an header, e.g. with tunnels. > > > > > > > > > > > > How about the other adjustments that Eric mentioned regarding the size > > > > > > of the buffer? Aren't they required? > > > > > > > > > > > > > > > > I guess that if stmmac_rx_buf1_len() needed such adjustment, it would > > > > > be already broken when XDP is in use. > > > > > When you use XDP, stmmac_rx_offset() adds a pretty big headroom of 256 > > > > > byte, which would easily trigger an overflow if not accounted. > > > > > Did you try attaching a simple XDP program on a stock 5.13 kernel? > > > > > > > > Yes, as mentioned in [1], to which you replied... > > > > > > > > M. > > > > > > > > [1] https://lore.kernel.org/r/87wnohqty1.wl-maz@kernel.org > > > > > > > > > > Great. > > > So I doubt that the adjustment is needed. > > > Does it work with all the frame size? > > > > I have no idea. Honestly, you are the one who should be able to answer > > these questions, given that you should have worked out how the buffer > > allocations work in this particular driver. > > > > This whole "let's try another random set of values until something > > sticks" is not how things ought to be done, and doesn't fill me with > > the utmost confidence that 5.14 (which apparently may well be cut in > > *two days*) is going to have a solid stmmac driver. > > > > I re-re-request that this patch gets reverted until you figure out > > what is wrong with the initial patch. > > > > Thanks, > > > > I would have done it, but I'll not have the hardware until next week at least, > otherwise I'd have tried all these tests myself. > > I'm sure that NET_SKB_PAD doesn't need to be there, if just removing > it fixes the problem, consider applying it and put a Fixes tag. No, I don't think that's the right thing to do. A patch breaks a driver, and the author of the patch is not in a position to fix it. That's OK, these things happen, it's just bad timing. But I don't understand this part of the kernel well enough to submit a patch based on a sample of *one*, at the last minute, just because "it works for me", and have the confidence that it doesn't break anything else. I have now posted a revert of the original patch[1]. I'll be happy to work with you, with a less pressure, in order to have something that works for everyone in the next cycle. Thanks, M. [1] https://lore.kernel.org/netdev/20210820183002.457226-1-maz@kernel.org -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv